1. Field of the Invention
This invention relates to a manufacturing method for semiconductor devices involving cleaning, and particularly relates to a manufacturing method for semiconductor devices involving cleaning process to remove residual particles on the semiconductor wafer surface.
2. Description of Related Art
A manufacturing method for semiconductor devices involving fine processing (LSI, VLSI and the like) has been developed. In this situation, a cleaning process for cleaning semiconductor devices is one of important processes in manufacturing process for improving manufacturing yield of semiconductor device. Cleaning is carried out as pre-treatment or aftertreatment of some processes such as film forming and etching.
Conventionally, semiconductor wafers (referred to as wafers hereinafter) are cleaned with pure water or diluted solution containing various acids or alkalis in pure water by means of dipping of wafer in the solution or spraying of the solution on wafer to clean off particles on the wafer surface. A method in which a wafer is dipped in a solution and the wafer surface is brushed mechanically in the solution has also been employed. Such cleaning method is called “wet cleaning” because of the fact that a solution is used.
However, wet cleaning requires subsequent rinsing and drying processes in addition to cleaning process to result in increased multi-step process. The multi-step process is a problem.
Dry cleaning has been known as cleaning method that solves the problem of wet cleaning.
One of the dry cleaning methods is disclosed in, for example, JP-A No. 131981/1996 (referred to as known literature 1 hereinafter). According to the known literature 1, an object to be cleaned, for example, a 6-inch silicon wafer for semiconductor that has been formed by slicing, lapping, and polishing a single crystal silicone, is cleaned with activated air at dry room temperature condition to remove particles adsorbed electrostatically on the object to be cleaned. In detail, the activated air contains air ions and water clusters to form high humidity atmosphere. The flowing activated air cleans an object to be cleaned in a cleaning chamber in contact with the object. The air ions neutralize electric charges of the object to be cleaned, and the water clusters isolate particles from the surface of the object to be cleaned. The flowing activated air peels off and removes particles. The known literature 1 discloses pre-treatment cleaning for LSI manufacturing that is carried out after purchase of Si wafer from a wafer maker in detail.
Another dry cleaning method is disclosed in JP-A No. 85887/1996 (referred to as known literature 2 hereinafter) According to the known literature 2, a W sample to be etched having single film or laminated film is etched, and then transferred to an aftertreatment equipment (treatment equipment used in the next process) by means of a vacuum transfer equipment. Resist and particles are removed (plasma ashing) together in the aftertreatment equipment (in vacuum) without exposing the sample in the atmosphere.
Yet another dry cleaning method is disclosed in JP-A No. 17776/1997 (referred to as known literature 3 hereinafter). According to the known literature 3, to form a film that is accessible to adsorbed organic substance on a semiconductor substrate when the film is formed, the film is cleaned with O3 in room temperature or high temperature condition in the same semiconductor manufacturing equipment to remove adsorbed organic substance before film forming of an under layer film and to thereby stabilize film forming that is sensitive to the surface condition of the semiconductor substrate. In other words, according to the known literature 3, O3 gas is introduced into the semiconductor manufacturing equipment that was used to form the under layer wiring pattern on the semiconductor substrate to clean the semiconductor substrate. At that time, O3 gas reacts with residual organic substance on the semiconductor surface, and the organic substance is removed in the form of volatile products such as CO or CO2.
Recently, system-on-chip (so-called system LSI) that is typical of job shop type product has become major instead of DRAM that is typical of less-item mass-production type product. The job shop type production regards short TAT (Turn Around Time) important to increase the production efficiency.
Hence it is required to employ dry cleaning process for cleaning that is carried out as pre-treatment or aftertreatment of semiconductor device manufacturing process.
High performance device requires new materials including hygroscopic film materials such as organic film that is so-called as Low-k film (low dielectric constant film having a dielectric constant of 3.0 or lower) and porous organic film such as interlayer dielectric. Wet cleaning and even the exposure to the atmosphere cause conversion of device quality in semiconductor device manufacturing process in which such new materials are used.